This application is based on application No. 2000-308483 filed in Japan, the content of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a map display device, a map display method, and a computer program for use in a map display device. The invention in particular relates to road map display techniques used in car navigation devices.
2. Related Art
Example applications for map display devices include a car navigation device. A map display device used in a car navigation device needs to enable a user, i.e. a driver, to comprehend a displayed map at a glance. Hence various map display techniques have been devised so that the driver can understand displayed information at once. One of such techniques is a method of emphasizing information which is likely to be desired by the driver.
When driving a car, there are some points to which the driver seems to pay particular attention, such as an intersection and a destination location. Such points are hereinafter called xe2x80x9cpoints of interestxe2x80x9d. A conventional type of map display device displays an enlarged view of a point of interest and its vicinity. For example, when a car is approaching a main intersection, this type of map display device displays an enlarged view of the intersection and its vicinity, to help the driver decide which route he or she should take. Here, the enlarged view may be displayed not on the whole screen but over a part of the screen so as to partially overlap the map which is being displayed on the screen.
Another type of map display device displays, over a part of a map which is being displayed on a screen, a wide area view of the periphery of an area covered by the map, on a smaller scale. This method allows the driver to consult the map, and at the same time consult the wide area view to check which roads exist around the area covered by the map.
Thus, conventional map display devices emphasize information which is likely to be desired by the driver, by displaying an enlarged view of the vicinity of a point of interest or a wide area view of the periphery of an area shown by a map. In this way, the driver can quickly comprehend information displayed on the screen.
However, when the enlarged view of the vicinity of the point of interest is displayed on the whole screen, the driver can view the enlarged view but cannot view the map of the area outside the vicinity of the point of interest, and therefore cannot check the roads existing around the vicinity of the point of interest.
Also, when the enlarged view of the vicinity of the point of interest or the wide area view of the periphery of the area covered by the map is displayed on part of the screen, the driver cannot view the part of the map which is concealed by this display. Besides, there is no continuity between the map and the enlarged or wide area view whose scale is different with the map. This makes it difficult for the driver to quickly comprehend the relation between the two maps displayed on the screen, in particular the connections of roads between these maps.
Also, the driver may lose sight of the point of interest, when moving his or her eyes between the map and the enlarged or wide area view.
There is also a conventional technique of displaying a map using the law of perspective. This method displays distant objects to be small and close objects to be large in accordance with human visual characteristics, thereby helping the driver view the map in the right perspective. However, when displaying the vicinity of the point of interest in enlarged view or the periphery of the area in wide area view, this technique has the same problem as above.
In view of the above problems, the present invention aims to provide a map display device that enables a driver to quickly and accurately comprehend the contents of a map displayed on a display screen.
(1) The stated object can be achieved by a map display device characterized by (a) generating surfaces with different shapes which are obtained in a process of gradually changing a curvature of a surface with time, (b) transforming first coordinate information that relates to a map, to second coordinate information on each of the generated surfaces, and (c) displaying the map in accordance with the second coordinate information on each of the generated surfaces.
According to this construction, the map can be displayed with a desired portion gradually enlarged or contracted, while maintaining connections of roads. For instance, it is possible to enlarge a point of interest and its vicinity on a map which the driver wants to consult closely, and at the same time contract the periphery of an area covered by the map so that the periphery is displayed in wide area view. As a result, the connections of roads are maintained, and the driver can accurately and quickly comprehend the contents of the map displayed on the display screen. Also, the map is displayed with its shape being changed gradually from one shape to another. This enables the map display to be transformed smoothly, even when the target of enlargement/contraction switches from one map portion to another. Hence the driver will not lose sight of the point of interest he or she is paying attention to on the map.
(2) The map display device of (1) may include: a map storing unit for storing the first coordinate information, the first coordinate information showing positions of objects in the map; a surface generating unit for generating the surfaces which are obtained in a process of gradually deforming the surface from a first shape to a second shape, the generated surfaces including (a) intermediate surfaces that each have an intermediate shape between the first shape and the second shape and (b) a surface that has the second shape; a mapping unit for (a) transforming the first coordinate information to the second coordinate information on each of the generated surfaces, and (b) texture-mapping graphics that represent the objects onto each of the generated surfaces with reference to positions shown by the second coordinate information, to obtain mapped images corresponding to the generated surfaces; and a projecting/displaying unit for perspective-projecting the mapped images sequentially onto a flat virtual screen to obtain projected images, and displaying the projected images in sequence.
(3) In the map display device of (2), the first shape and the second shape may be (a) a flat surface and a curved surface, (b) a curved surface and a flat surface, or (c) two curved surfaces.
According to these constructions, the mapped images on the generated surfaces are perspective-projected on the flat virtual screen. As a result, each projected image is displayed with an enlarged or contracted portion, unlike the case where the map is simply perspective-projected onto the flat virtual screen. Also, since the shapes of the generated surfaces are spatially continuous, the connections of roads are maintained through the projected images. With these features, the map display device produces the above effects.
(4) In the map display device of (2), a portion of the map that includes a point of interest may need to be enlarged or contracted gradually with time, wherein the surface generating unit (a) generates, when the portion needs to be enlarged, the surfaces where the second shape is defined such that: an angle formed between a part of the surface with the second shape to which graphics which represent objects included in the portion are texture-mapped and a line of sight directed to the part of the surface in the perspective projection is larger than any angles formed between other parts of the surface and lines of sight directed to the other parts of the surface in the perspective projection, and (b) generates, when the portion should be contracted, the surfaces where the second shape is defined such that: an angle formed between a part of the surface with the second shape to which graphics which represent objects included in the portion are texture-mapped and a line of sight directed to the part of the surface in the perspective projection is smaller than any angles formed between other parts of the surface and lines of sight directed to the other parts of the surface in the perspective projection.
(5) In the map display device of (4), the surface generating unit may include: a point accepting unit for accepting an indication of a position of the point of interest and an indication regarding whether the portion including the point of interest should be enlarged or contracted, from a user, wherein the surface generating unit generates the surfaces in accordance with the accepted indications.
According to these constructions, when the driver indicates the position of the point of interest, the map portion including the point of interest is enlarged or contracted gradually. For instance, by indicating an intersection to be enlarged gradually, the driver can view the intersection and its vicinity closely. Also, by indicating the periphery of the map to be contracted gradually, the driver can view the periphery in wide area view. The display is transformed gradually in both cases, so that the driver will not lose sight of the point of interest he or she is paying attention to on the map.
(6) The map display device of (5) may further include: an altitude storing unit for storing altitude information showing a correspondence between positions of points in the map and altitudes of the points, wherein the mapping unit includes: a surface deforming unit for (a) transforming the positions shown by the altitude information to positions on each of the generated surfaces, and (b) providing undulations corresponding to the altitudes shown by the altitude information, to each of the generated surfaces at the transformed positions, to generate deformed surfaces, and the mapping unit transforms the first coordinate information to the second coordinate information on each of the deformed surfaces.
According to this construction, the map display device displays the map of three-dimensional appearance in accordance with the altitudes, so that the map which delivers the same degree of realism as the view when looking at the actual terrain from the sky can be presented to the driver. Thus, in addition to the above effects, the driver""s understanding of the topography is facilitated.
(7) In the map display device of (6), the surface deforming unit may include: an altitude changing unit for changing altitudes in the altitude information that correspond to positions which belong to a first area in the map, to a uniform value, the first area being made up of a current position of the map display device and a neighborhood thereof, wherein the surface deforming unit generates the deformed surfaces using the changed altitude information.
According to this construction, the map display device displays the vicinity of the car position flatly and the other area three-dimensionally. Accordingly, in addition to the above effects, the display of the vicinity of the car position is kept from being obstructed by undulations.
(8) In the map display device of (7), the altitude changing unit may further change altitudes in the altitude information that correspond to positions which belong to an area around the first area in the map, in accordance with distances of the positions from the first area.
According to this construction, the boundary area between the flatly displayed area and the three-dimensionally displayed area is displayed so that the flat area and the three-dimensional area show continuity. Accordingly, in addition to the above effects, unnaturalness in visuality is reduced.
(9) In the map display device of (2), when sequentially displaying the projected images, the projecting/displaying unit may also display character strings that show the objects, with reference to display positions of the graphics that represent the objects.
According to this construction, the map display device does not subject character fonts to texture mapping and perspective projection, but directly displays the character fonts at the corresponding position on the display screen. As a result, the deformation of the character fonts due to texture mapping and perspective projection is avoided, with it being possible to increase the character viewability.
(10) The map display device of (1) may include: a map storing unit for storing the first coordinate information, the first coordinate information showing positions of objects in the map; a surface generating unit for generating the surfaces which are obtained in a process of gradually deforming the surface from a first shape to a second shape, the generated surfaces including (a) intermediate surfaces that each have an intermediate shape between the first shape and the second shape and (b) a surface that has the second shape; and a projecting/displaying unit for (a) transforming the first coordinate information to the second coordinate information on each of the generated surfaces, (b) perspective-projecting graphics that represent the objects onto each of the generated surfaces which serve as virtual screens with reference to positions shown by the second coordinate information, to obtain projected images corresponding to the generated surfaces, and (c) displaying the projected images in sequence.
(11) In the map display device of (10), the first shape and the second shape may be (a) a flat surface and a curved surface, (b) a curved surface and a flat surface, or (c) two curved surfaces.
According to these constructions, the map is perspective-projected onto the generated surfaces. As a result, each projected image is displayed with an enlarged or contracted portion, unlike the case where the map is simply perspective-projected onto a flat virtual screen. Also, since the shapes of these generated surfaces are spatially continuous, the connections of roads are maintained through the projected images. Hence the above effects are achieved.
(12) In the map display device of (10), a portion of the map that includes a point of interest may need to be enlarged or contracted gradually with time, wherein the surface generating unit (a) generates, when the portion needs to be enlarged, the surfaces where the second shape is defined such that: an angle formed between a part of the surface with the second shape to which graphics which represent objects included in the portion are perspective-projected and a line of sight directed to the part of the surface in the perspective projection is smaller than any angles formed between other parts of the surface and lines of sight directed to the other parts of the surface in the perspective projection, and (b) generates, when the portion needs to be contracted, the surfaces where the second shape is defined such that: an angle formed between a part of the surface with the second shape to which graphics which represent objects included in the portion are perspective-projected and a line of sight directed to the part of the surface in the perspective projection is larger than any angles formed between other parts of the surface and lines of sight directed to the other parts of the surface in the perspective projection.
(13) In the map display device of (12), the surface generating unit may include: a point accepting unit for accepting an indication of a position of the point of interest and an indication regarding whether the portion including the point of interest should be enlarged or contracted, from a user, wherein the surface generating unit generates the surfaces in accordance with the accepted indications.
According to these constructions, when the driver indicates the position of the point of interest, the map portion including the point of interest is gradually enlarged or contracted. For instance, by indicating an intersection to be enlarged gradually, the driver can view the intersection and its vicinity closely. Also, by indicating the periphery of the map to be contracted gradually, the driver can view the periphery in wide area view. The display is transformed gradually in both cases, so that the driver will not lose sight of the point of interest he or she is paying attention to on the map.
(14) The map display device of (13) may further include: an altitude storing unit for storing altitude information showing a correspondence between positions of points in the map and altitudes of the points, wherein the projecting/displaying unit includes: a map deforming unit for (a) calculating altitudes at the positions shown by the first coordinate information, based on the altitude information, and (b) changing the first coordinate information according to the calculated altitudes, and the projecting/displaying unit transforms the changed first coordinate information to the second coordinate information on each of the generated surfaces.
According to this construction, the map display device displays the map of three-dimensional appearance in accordance with the altitudes, so that the map which delivers the same degree of realism as the view when looking at the actual terrain from the sky can be presented to the driver. Thus, in addition to the above effects, the driver""s understanding of the topography is facilitated.
(15) In the map display device of (14), the map deforming unit may include: an altitude changing unit for changing altitudes shown by the altitude information that correspond to positions which belong to a first area in the map, to a uniform value, the first area being made up of a current position of the map display device and a neighborhood thereof, wherein the map deforming unit changes the first coordinate information in accordance with the changed altitude information.
According to this construction, the map display device displays the vicinity of the car position flatly and the other area three-dimensionally. Accordingly, in addition to the above effects, the display of the vicinity of the car position is kept from being obstructed by undulations.
(16) In the map display device of (15), the altitude changing unit may further change altitudes shown by the altitude information that correspond to positions which belong to an area around the first area in the map, in accordance with distances of the positions from the first area.
According to this construction, the boundary area between the flatly displayed area and the three-dimensionally displayed area is displayed so that the flat area and the three-dimensional area show continuity. Accordingly, in addition to the above effects, unnaturalness in visuality is reduced.
(17) In the map display device of (10), when sequentially displaying the projected images, the projecting/displaying unit may also display character strings that show the objects, with reference to display positions of the graphics that represent the objects.
According to this construction, the map display device does not subject character fonts to perspective projection, but directly displays the character fonts at the corresponding position on the display screen. As a result, the deformation of the character fonts due to perspective projection is avoided, with it being possible to increase the character viewability.
(18) The above object can also be achieved by a map display device characterized by (a) transforming, when a position of a point of interest on a map is indicated by a user, first coordinate information which relates to the map to second coordinate information on a curved surface whose shape corresponds to the indicated position, and (b) displaying the map according to the second coordinate information.
According to this construction, when the driver indicates the position of the point of interest on the map, the map display device displays the map in which a portion including the point of interest is enlarged or contracted.
(19) The above object can also be achieved by a map display method including: a surface generating step for generating surfaces which are obtained in a process of gradually deforming a surface from a first shape to a second shape, the generated surfaces including (a) intermediate surfaces that each have an intermediate shape between the first shape and the second shape and (b) a surface that has the second shape; a mapping step for (a) transforming first coordinate information to second coordinate information on each of the generated surfaces, the first coordinate information showing positions of objects in a map, and (b) texture-mapping graphics that represent the objects onto each of the generated surfaces with reference to positions shown by the second coordinate information, to obtain mapped images corresponding to the generated surfaces; and a projecting/displaying step for perspective-projecting the mapped images sequentially onto a flat virtual screen to obtain projected images, and displaying the projected images in sequence.
(20) The above object can also be achieved by a map display method including: a surface generating step for generating surfaces which are obtained in a process of gradually deforming a surface from a first shape to a second shape, the generated surfaces including (a) intermediate surfaces that each have an intermediate shape between the first shape and the second shape and (b) a surface that has the second shape; and a projecting/displaying step for (a) transforming first coordinate information to second coordinate information on each of the generated surfaces, the first coordinate information showing positions of objects in a map, (b) perspective-projecting graphics that represent the objects onto each of the generated surfaces which serve as virtual screens with reference to positions shown by the second coordinate information, to obtain projected images corresponding to the generated surfaces, and (c) displaying the projected images in sequence.
According to these constructions, the map is displayed with a desired portion gradually enlarged or contracted, while maintaining connection of roads. Hence the driver can quickly and accurately comprehend the contents of the map. Also, the map display is transformed smoothly even when the target of enlargement/contraction switches from one map portion to another, so that the driver will not lose sight of the point of interest he or she is paying attention to on the map.
(21) The above object can also be achieved by a computer-readable program for realizing a map display method on a computer, including: a surface generating step for generating surfaces which are obtained in a process of gradually deforming a surface from a first shape to a second shape, the generated surfaces including (a) intermediate surfaces that each have an intermediate shape between the first shape and the second shape and (b) a surface that has the second shape; a mapping step for (a) transforming first coordinate information to second coordinate information on each of the generated surfaces, the first coordinate information showing positions of objects in a map, and (b) texture-mapping graphics that represent the objects onto each of the generated surfaces with reference to positions shown by the second coordinate information, to obtain mapped images corresponding to the generated surfaces; and a projecting/displaying step for perspective-projecting the mapped images sequentially onto a flat virtual screen to obtain projected images, and displaying the projected images in sequence.
(22) The above object can also be achieved by a computer-readable program for realizing a map display method on a computer, including: a surface generating step for generating surfaces which are obtained in a process of gradually deforming a surface from a first shape to a second shape, the generated surfaces including (a) intermediate surfaces that each have an intermediate shape between the first shape and the second shape and (b) a surface that has the second shape; and a projecting/displaying step for (a) transforming first coordinate information to second coordinate information on each of the generated surfaces, the first coordinate information showing positions of objects in a map, (b) perspective-projecting graphics that represent the objects onto each of the generated surfaces which serve as virtual screens with reference to positions shown by the second coordinate information, to obtain projected images corresponding to the generated surfaces, and (c) displaying the projected images in sequence.
According to these constructions, the above effects can be delivered.